Testing the association between human mid-facial morphology and climate using autosomal, mitochondrial, Y chromosomal polymorphisms and cranial non-metrics

Inferring human neutral genetic variation from craniodental phenotypes

There is a growing consensus that global patterns of modern human cranial and dental variation are shaped largely by neutral evolutionary processes, suggesting that craniodental features can be used as reliable proxies for inferring population structure and history in bioarchaeological, forensic, and paleoanthropological contexts. However, there is disagreement on whether certain types of data preserve a neutral signature to a greater degree than others. Here, we address this unresolved question and systematically test the relative neutrality of four standard metric and nonmetric craniodental data types employing an extensive computational genotype-phenotype comparison across modern populations from around the world. Our computation draws on the largest existing data sets currently available, while accounting for geographically structured environmental variation, population sampling uncertainty, disparate numbers of phenotypic variables, and stochastic variation inherent to a neutral model of evolution. Our results reveal that the four data types differentially capture neutral genomic variation, with highest signals preserved in dental nonmetric and cranial metric data, followed by cranial nonmetric and dental metric data. Importantly, we demonstrate that combining all four data types together maximizes the neutral genetic signal compared with using them separately, even with a limited number of phenotypic variables. We hypothesize that this reflects a lower level of genetic integration through pleiotropy between, compared to within, the four data types, effectively forming four different modules associated with relatively independent sets of loci. Therefore, we recommend that future craniodental investigations adopt holistic combined data approaches, allowing for more robust inferences about underlying neutral genetic variation.

The Bronze and Iron Age populations of the Armenian Highland in the genetic history of Armenians

OBJECTIVES

To investigate the biological diversity of the late Bronze and Iron Age populations in the Armenian Highland by nonmetric cranial traits, evaluate the genetic continuity in the development of the modern Armenian gene pool, and compare the results obtained with genetic data.

MATERIALS AND METHODS

Twenty-eight nonmetric cranial traits were scored on 498 adult crania from different late Bronze and Iron Age cemeteries, as well as from modern Armenians and other European populations. We carried out a biodistance analysis between populations using the mean measure of divergence (MMD) statistics, tested the spatial-temporal model of population structure, and assessed the diversity within the late Bronze and early Iron Ages by using the values of variability index (Fst).

RESULTS

The biodistance analysis revealed a close relationship among different ancient Armenian populations and between the average frequencies of the three sequential periods (late Bronze Age, early Iron Age I and II) and modern Armenians. A gradual increase of variability (Fst) within the three successive periods was observed.

DISCUSSION

The analysis of nonmetric trait data reflects deep roots and continuity in the formation of the Armenian population. Since at least the Late Bronze Age, owing to permanent isolation, no significant changes have occurred in the Armenian gene pool. An increase in variability over the successive periods reflects the process of population differentiation from a single gene pool while maintaining average trait frequencies. The congruence of the results obtained with the genetic data confirms, once more, the possibility of using nonmetric cranial traits as a proxy for genetic markers.

The prevalence of under-nutrition among the tribal children in India: a systematic review

Tribal population of India constitutes 8.6% of the total population. They are more susceptible to undernutrition which is recognized as a prevalent health problem mainly because of their uncertainty of food supply, which has serious long term consequences for the child and adversely influences the development of the nation. The assessment of nutritional status is paramount importance because it impels to identify malnutrition which is an aggravation of morbidity and mortality. This review was aimed to find out the overall nutritional status of tribal preschool children. It also seek the major socio-cultural causes which influence the nutritional status from bio-cultural perspectives among the tribal children in India in order to make foundation of new research. In the present review, 41 papers on nutritional status of tribal preschool children published from January 1st 2000 till date, have been identified and included for analysis. To analyze the data, meta-analysis was done using MedCalc software.

The meta-analysis revealed the average rate of prevalence of underweight, stunting and wasting among the preschool tribal children of India was 42.96%; 44.82% and 23.69%. Among the 41 different studies these rates vary among the different tribal groups of different states associated with their socio-economic status (10%), their cultures of food consumption (10%), maternal education (15%), child feeding practices (20%), dietary deficit during pregnancy (25%) and poor nutrition of the child (52%).

Prevalence rate of under-nutrition and stunting is relatively high in comparison to WHO in India whereas, rate of wasting was lower in comparison to national level which reflect that immediate nutritional status was poor but chronic deficiency of nutrition was less. Nutritional education and short term appropriately planned nutritional intervention programs may also be useful for enhancing their nutritional status.

Non-metric traits, physiological stress indicators and paleopathological lesion on human skeletal remains from an early modern cemetery in Wyszyński Street, Wrocław, Poland (15th–18th centuries AD)

The anthropological analysis and assessment of the living conditions of historical populations should be comprehensive. Due to the scarcity of the well-preserved skeletal remains of a population buried at the cemetery in Wyszyński Street, Wrocław, each piece of information is particularly important in providing the complementary information about living and health conditions of late medieval and early modern inhabitants of Wrocław. This study aims to assess the living conditions of the late medieval and early modern Wrocław inhabitants. This aim was reached by analyzing the frequency of non-metrical cranial and postcranial traits, physiological stress indicators, and pathological lesions. The importance of these traits for population studies is also discussed. For 98 skeletons (22.4% male and 37.8% female) from a cemetery located in Wyszyński Street, (15th –18th centuries AD), the frequencies (p) of the following traits were analyzed: 38 non-metric cranial and 9 post-cranial traits, the morphological indicators of physiological stress (i.e. cribra orbitalia and enamel hypoplasia), caries and pathological lesions on bones. Among the non-metric cranial traits, only nine (23.7%) were not observed. The most frequent (from p= 0.30 to p=0.65) were foramen parietale, incisura frontalis accesoria seu foramen frontale accesorius, foramen supraorbitale, M3 mandibulare, ossicula suturae lambdoideae, and foramen mastoideum extrasuturale. Only three non-metric post-cranial traits were observed, but with low frequency (p=0.01 and 0.02). Cribra orbitalia was present in 37.0% of the skeletons while enamel hypoplasia was present in only 2.6%. Susceptibility to caries occurred in 68% of the cases while carries lesions occurred in 31.2%. Among pathological changes, the most frequent were degenerative changes (21.6%) and injuries (19.6%). Owing to the poorly preserved remains, the complete assessment of the living conditions of the population was difficult. The number of the observed traits would have probably increased, had the number of complete and well-preserved skeletons been higher. The results of the study suggest that the living conditions of the studied population were poor. It is hypothesized that the cemetery was a burial place for prisoners and victims of various epidemics that affected the city. But since the historical sources of this cemetery are scarce, it is hard to unequivocally state its purpose with certainty.

Nasal cavity and maxillary sinuses form variation among modern humans of Asian descent

OBJECTIVES

This study explores variation, covariation, and ecogeographic pattern of the nasal cavity, maxillary sinuses, and external midfacial skeleton across 15 populations of east Asian origin inhabiting the Far East, Siberia, Alaska and Greenland.

MATERIALS AND METHODS

We have collected linear measurements of the internal nasal cavity, maxillary sinus and external midfacial skeleton as well as volumes and surface areas of three-dimensional models of the cavity. A set of seven climatic variables, mtDNA and Y-chromosome genetic matrices and a matrix of geographic distances were also utilized.

RESULTS

A strong association between form of the nasal cavity and climate was found, whereby all north Asian groups display increased volumes, areas and lengths of the cavity, and surface area to volume ratios (SA/V). Most of Siberian groups exhibit not only large and long, but also wide and tall nasal cavity. The Eskimo-Aleutian speaking groups possess cavities that are vertically short and narrow but of a high SA/V ratio. The sinuses exhibit an exceptionally high level of within- and between-group variation which supports the views on the sinus as an architectural byproduct. Both volume and area of the nasal cavity can be reliably estimated based on a set of simple and repeatable linear measurements.

DISCUSSION

While the nasal cavity and maxillary sinus are both larger in a larger facial skeleton, there is a strong inverse relationship between them at a given facial size. Our results do not support the notion that the shape of the internal nasal cavity is more strongly associated with climate compared to the external midfacial morphology.

Moderate climate signature in cranial anatomy of late holocene human populations from Southern South America

OBJECTIVE

The aim of this study is to analyze the association between cranial variation and climate in order to discuss their role during the diversification of southern South American populations. Therefore, the specific objectives are: (1) to explore the spatial pattern of cranial variation with regard to the climatic diversity of the region, and (2) to evaluate the differential impact that the climatic factors may have had on the shape and size of the diverse cranial structures studied.

MATERIALS AND METHODS

The variation in shape and size of 361 crania was studied, registering 62 3D landmarks that capture shape and size variation in the face, cranial vault, and base. Mean, minimum, and maximum annual temperature, as well as mean annual precipitation, but also diet and altitude, were matched for each population sample. A PCA, as well as spatial statistical techniques, including kriging, regression, and multimodel inference were employed.

RESULTS

The facial skeleton size presents a latitudinal pattern which is partially associated with temperature diversity. Both diet and altitude are the variables that mainly explain the skull shape variation, although mean annual temperature also plays a role. The association between climate factors and cranial variation is low to moderate, mean annual temperature explains almost 40% of the entire skull, facial skeleton and cranial vault shape variation, while annual precipitation and minimum annual temperature only contribute to the morphological variation when considered together with maximum annual temperature. The cranial base is the structure less associated with climate diversity.

CONCLUSION

These results suggest that climate factors may have had a partial impact on the facial and vault shape, and therefore contributed moderately to the diversification of southern South American populations, while diet and altitude might have had a stronger impact. Therefore, cranial variation at the southern cone has been shaped both by random and nonrandom factors. Particularly, the influence of climate on skull shape has probably been the result of directional selection. This study supports that, although cranial vault is the cranial structure more associated to mean annual temperature, the impact of climate signature on morphology decreases when populations from extreme cold environments are excluded from the analysis. Additionally, it shows that the extent of the geographical scales analyzed, as well as differential sampling may lead to different results regarding the role of ecological factors and evolutionary processes on cranial morphology.

Environment-Related Variation in the Human Mid-Face

Previous studies that have examined mid-facial morphology in geographically dispersed and genetically diverse groups of humans have shown a strong adaptation of the nasal part to extreme cold environments, which was not observed in non-Arctic regions. However, it remains unclear whether different parts of the mid-face area show independent adaptation to nonpolar climates, and if so, how this adaptation impacted the morphology. To address this question, we investigated potential associations between climatic variables and the mid-facial shape in 14 populations, focusing on four aspects of the morphology: total shape, zygomatic, nasal and alveolar. The results show that when the genetic distance between populations is not considered, all aspects of the morphology are strongly correlated with all climatic variables. When the genetic distance is considered, significant correlations remain only for the zygomatic, and nasal parts with temperature, and for the nasal part and alveolar with sunshine exposure. A strong but probably artificial correlation of the alveolar with atmospheric pressure is also observed. Additionally, partial least square analyses indicate that tropical and subtropical environments are associated with smaller zygomatic and more triangular nose aperture compared to more temperate environments. These findings suggest that temperate and tropical climates have induced adaptation of zygomatic and nasal parts of the mid-face in humans, and that this adaptation was probably driven by temperature and sunlight exposure conditions. Anat Rec, 300:238-250, 2017. © 2016 Wiley Periodicals, Inc.

The association between mid-facial morphology and climate in northeast Europe differs from that in north Asia: Implications for understanding the morphology of Late Pleistocene Homo sapiens

The climate of northeastern Europe is likely to resemble in many ways Late Pleistocene periglacial conditions in Europe, but there have been relatively few studies exploring the association between climate and morphology in the mid-face of modern northeastern European populations. To fill this gap, we sampled 540 male skulls from 22 European and Near Eastern groups, including 314 skulls from 11 populations from northeastern Europe, to test for possible climate-morphology association at the continental scale. Our results found a moderate and highly significant association (R = 0.48, p = 0.0013, Mantel test) between sets of 23 mid-facial measurements and eight climatic variables. A partial least squares analysis revealed this association to be mostly driven by differences between groups from northeastern Europe and populations from the Mediterranean and the Caucasus. Matrices of between-group genetic distances based on Y-chromosome and mtDNA markers, as well as cranial non-metric and geographic distance matrices, were used to control for the possible influence of shared population history. Irrespective of which measure of neutral between-population distances is taken into account, the association between cranial variables and climate remains significant. The pattern of association between climate and morphology of the mid-face in western Eurasia was then compared to that in east and north Asia. Although differences between the two were found, there were also similarities that support existing functional interpretations of morphology for the bony parts of the upper airways. Last, in a preliminary analysis using a reduced set of measurements, mid-facial morphology of several Upper Paleolithic European Homo sapiens specimens was found to be more similar to groups from northern and northeastern Europe than to southern European populations. Thus, the population of northeastern Europe rather than east and north Asian groups should be used as a model when studying climate-mediated mid-facial morphology of Upper Paleolithic European H. sapiens.

Ancestry Estimation Using Macromorphoscopic Traits

Anthropologists have a lengthy history using cranial nonmetric traits to assess biological distances between populations. These concepts were adopted by forensic anthropologists to estimate ancestry at the individual level using population-based human variation. However, this method of estimation must adhere to the Daubert guidelines to be applied in the modern court system. To that end, a set of cranial macromorphoscopic traits have been proffered to generate a methodological approach to the estimation of ancestry that can be empirically tested and verified. Additionally, various statistical frameworks, parametric and nonparametric, have been employed to calculate error rates and provide probabilistic statements of the strength of these estimations. Recent studies have further advanced the reliability and validity of macromorphoscopic trait analysis through reference datasets, validation studies, and demonstrable exploration of the complex population histories impacting human variation between and within populations worldwide.